Will leaving the laptop power brick connected to the power socket be dangerous?

Can I flip this around and ask why you think it is dangerous?

Is it the danger of it bursting into flames? (Miniscule) Is it the heat given off by the brick perhaps melting nearby items? (Maybe - chocolate?) Is it the trip hazard from the cables? (On a desk?) Is it the untidiness? (People are messy...) Is it the energy waste? (~1W from this Coding Horror post)

None of those strike me as 'dangerous'. Sorry.

The amount of power consumed by the adapter when the laptop is not drawing any load is minimal. There's the parasitic power losses involved in having the voltage converter produce its output voltage, but without the laptop there's no real current being drawn from the wall.

The only things drawing power when the laptop is not plugged in are the resistive elements and diodes in the adapter itself. What about leaving the adapters plugged in do you think is dangerous?

as long as the power supply gets warm/hot despite unused, you've got a brilliant argument for energy saving.